The present invention relates generally to crash pads for transportation vehicle seats and more specifically to a crash pad that meets the Department of Transportation Head Injury Criterion for vehicle seats.
In recent years, efforts have been made to improve the crash worthiness of mass transportation vehicles such as school buses, city and interstate buses, trains and aircraft. Crash studies particularly in the ground transportation industry have shown that one of the major causes of injury to passengers in an accident is the result of being impacted or thrown into the vehicle seat structures. In a conventional mass transportation vehicle such as a bus, passengers are thrown from their seats forwardly into the next adjacent seat.
In the mass transportation industry and in particular in buses, active restraint systems such as seat belts have not received ready acceptance, due primarily to the nature of the vehicles involved and their uses. Thus, the trend, particularly in buses, has been to provide for crash worthiness with passive restraint systems. Most recently, these efforts have been directed to arranging the interiors of the vehicles so that the passengers are compartmentalized in a fore and aft direction by pairs of vehicle seats. The design emphasis on the seats themselves is to provide a seat which is capable of absorbing impact energy in a controlled manner within certain levels so as to reduce or prevent the occurrence of, and severity of injuries to the passengers. In an accident, a passenger typically will be hurdled forward, first impacting the seat in front of him with his knees. Next, the head of the passenger will impact the upper portion of the rear surface of the seat back and this impact is followed by a full body impact against the back of the seat.
In an effort to provide crash protection and in accordance with the mandate set forth in the National Motor Vehicle Safety Act of 1966, 15 USC s/s 1381 et seq., as amended by Public Law 93-492 in 1974, the Department of Transportation issued design specifications which set forth certain criteria relating to energy absorbtion and compartmentalization characteristics which must be met by public mass transportation vehicle seating. With regard to the energy absorbing characteristics of the barrier or seat used to restrain the passengers, they must meet three basic requirements. First, the barrier must provide an energy absorbing structure that prevents the force applied to an occupant impacting the barrier from exceeding a limit that would cause internal injuries. The second and third requirements are impact zone criterion for the head and legs. According to these impact zone criterion, surfaces of the barrier contacted by the legs and head of the passenger during impact must meet separate energy absorbtion requirements that prevent the knees or head of the occupant from receiving a damaging spike of force.
The use of mere padding to meet Head Injury Criterion is unsuitable because of the bulk of the padding required to meet the criterion. Furthermore, padded seats are undesirable since they are often the object of vandalism. Not only is the vandalized seat unsightly, but once cut, the padding often loses its effectiveness and the seat no longer meets head injury criterion. In one prior art arrangement, a plastically deformable metal panel was secured to the seat back for yielding and absorbing large amounts of energy during the blow. However, when such a crash pad was provided, a problem was presented by the panel itself presenting exposed metal edges, exposed fasteners and the like. Thus, even where a deformable metal panel was provided, the panel was covered with a layer of cushioning material or padding which is easily vandalized.